I'm developing a game for Android. For the purpose of this question lets assume please that I have a sprite of red ball moving in space over some background of whatever. I have a PNG file which I use to draw my background and a PNG file which I use to draw my ball over the background. Problem is my ball is a red circle on a 20 X 20 pixels PNG, meaning I have some white 'left over', so when I draw it on the screen, the 'white left over' appears over my background when I only want the red circle to.

I'm sorry but I'm totally new to animation. How do I crop my circle out of my square PNG or otherwise make the background in my ball PNG transparent ??? Do I do it programmatically or is there a way to paint my PNG so the non relevant part is transparent ?

I know this question is old but if someone new comes to see this with the same question I suggest you use paint.net You can use the magic wand to select the area you want to make transparent and then press "cut"(the scissor symbol) or press CTRL+X